This proposal describes a planning grant for a clinical trial of an intervention to prevent dental caries in caries-active adults. Little information is available about the effectiveness of caries prevention methods in adults, and virtually no information exists with respect to prevention among adults who are most likely to experience carious lesions. Recent recommendations from the Centers for Disease Control and an NIH Consensus Development Conference on dental caries both call for trials of caries prevention methods in caries active adults. The planning grant is requested principally to develop a Manual of Procedures for the proposed trial. In addition, the planning period will permit refinements in planned approaches to participant recruitment, to maximizing and assessing adherence, and to analyses of caries increment data. The planning period is two years, and the planning activities involve personnel from both proposed clinical centers and the data coordinating center. The proposed clinical trial is envisioned as a three-year, two-center trial placebo-controlled randomized clinical trial. The intervention is the daily use of xylitol lozenges. Participants will be adults (25+) with current or recent caries lesions who are patients of one of the clinical centers. This intervention is being tested because it represents a potentially effective caries prevention method with a reasonably high likelihood of adoption by dental practitioners as an "add on" caries preventive method for caries-active patients, a group that current data suggests may be underexposed to caries-preventive treatment in dental practices. [unreadable] [unreadable]